Posted
by
Hemos
on Monday February 09, 2004 @05:05PM
from the what-then dept.

sonar67 writes "According to The Economist: 'It was beautiful, complex and wrong. In 150AD, Ptolemy of Alexandria published his theory of epicycles--the idea that the moon, the sun and the planets moved in circles which were moving in circles which were moving in circles around the Earth. This theory explained the motion of celestial objects to an astonishing degree of precision. It was, however, what computer programmers call a kludge: a dirty, inelegant solution. Some 1,500 years later, Johannes Kepler, a German astronomer, replaced the whole complex edifice with three simple laws. Some people think modern astronomy is based on a kludge similar to Ptolemy's. At the moment, the received wisdom is that the obvious stuff in the universe--stars, planets, gas clouds and so on--is actually only 4% of its total content. About another quarter is so-called cold, dark matter, which is made of different particles from the familiar sort of matter, and can interact with the latter only via gravity. The remaining 70% is even stranger. It is known as dark energy, and acts to push the universe apart. However, the existence of cold, dark matter and dark energy has to be inferred from their effects on the visible, familiar stuff. If something else is actually causing those effects, the whole theoretical edifice would come crashing down.'"

That is, of course, if we keep testing it and trying to see if it is true. (Or the closest approximation of 'true' we have been able to come up with.)

It matters now if it is not true because then we know we need a better theory. And that means we either didn't understand something we thought we understood, or that we hadn't explored our understanding fully. Either way, there is likely something else that will be affected...

That is, of course, if we keep testing it and trying to see if it is true. (Or the closest approximation of 'true' we have been able to come up with.)

You're absolutely correct. If we accepted theory as fact without any repeatable testing it would be religion, not science.

We may never fully understand the nature of our universe, and almost certainly will never understand it in our lifetimes. But the question raised in the topic is actually a fundamental one that spans far beyond dark matter to all forms of theoritical science. Many theories are based heavily upon other theories. The "root" theories (with any luck) will eventually be proven or disproven, affecting all research and theories which follow that "root".

What is important is for scientists to fully understand the theories that they base their work upon, and knowing the risks involved. Not doing so is irresponsible, and can lead to misinformation and confusion.

With the above in mind, it's also important to note that many theories have been disproven throughout and entire scientific disciplines have crumbled around the fall of these theories. However, from those ashes, new disciplines have arisen (the first that comes to mind is chemistry rising from the "ashes" of alchemy). I'm sure that in 100 years, many if our current ideas will be laughable, but this failure has proven fundamental to our growth (how's that for rhetoric!?)

Well actually knowledge of its existence and how much of it exists will determine whether or not the Universe eventually implodes on itself in the "Big Crunch" or whether the universe will keep expanding at the speed of light forever. So technically speaking, "in the long run" it will matter quite a bit:) Regards,Steve

knowledge of its existence and how much of it exists will determine whether or not the Universe eventually implodes on itself
I think it's safe to say that our knowing ANYTHING about dark or exotic matter will have no effect whatsoever on the fate of the universe.

There is a theory which states that if anyone discovers just exactly what the universe is for and why we are here, that it will instantly disappear and be replaced by something even more bizarre and inexplicable.

You can write a "hello world" program in
most programming languages in under ten lines
of code.

You could also write a program to synthesize
speech to say "hello world" in an MP3, rip the
MP3 to a wav file, and then write a speech-to-text
engine to finally dump "hello world" to the
screen.

Same idea here. Kepler's laws reduced a
nightmarish tangle of mathematics to a three
line "program", if you will. Out current model
of how various things in our universe interact
requires a degree in cosmology to fully grasp,
and a PhD to do any meaningful work in. Imagine
reducing that to one chapter of a freshman-level
physics or astronomy course.

So, it matters for that reason.
Unneccessary complexity slows down work in
the field, and in the long run can actually
prove counterproductive to the field as a
whole (think about it - 1500 years wasted
trying to make epicycles work).

Same idea here. Kepler's laws reduced a nightmarish tangle of mathematics to a three line "program", if you will. Out current model of how various things in our universe interact requires a degree in cosmology to fully grasp, and a PhD to do any meaningful work in. Imagine reducing that to one chapter of a freshman-level physics or astronomy course.

Einstein's Special and General Relativity, Maxwell's Equations, and Schrodinger's Equation are all expressed in a few lines of equations. But you need extensive math and physics training to relate them to the familiar world around us. Simple doesn't mean easy. Theoretical physicists are already busily looking for theoretical formulations in which dark matter and dark energy arise naturally, rather than as a kluge. Of course, if the original observations turn out to have been misinterpreted, they may be wasting their time.

I always thought this was an interesting an odd part of modern science and cosmology. Why should we assume occam's razor, that simpler explanations are better? Why should the universe be simple and elegant?

You have misunderstood Occam's razor. It doesn't say that at all.

Occam's razor, in its original form, translates to "Do not multiply entities unnecessarily". That has been modernized to "The simplest explanation is usually correct", which is close, but not exactly the same.

What Occam's razor really means is: given two (or more) possible explanations of a phenomenon, with no evidence favoring one over the other, assume that the simplest one is correct.

For instance, if I find a pinecone lying on the ground under a pine tree, the simplest explanation is that it fell off of the pine tree. Sure, it might have been planted there by invisible space aliens in conjunction with the Illuminati acting in strict accordance with the Masonic doctrine of the Coming of the Pine Cone King, but since there is no evidence to favor one explanation over the other, I should assume that it fell off of the pine tree.

That doesn't mean that it did fall off the pine tree, and it doesn't mean that I might not change my mind as more evidence is found. It also doesn't mean that I shouldn't look for more evidence and try to determine the origin of the pine cone with greater accuracy. That isn't what it says at all. It just means that until such evidence arises which would cause me to revise my view of things, I should assume the simplest explanation that fits the facts. The explanation should only change when the known facts do, or a better explanation is found.

It is quite obvious to me that the Earth is motionless and the Sun rotates around the Earth. Seems like a nice simple theory.

It is a nice simple theory, and it's one that worked for humanity for quite a long time. However, that theory becomes less and less simple as you try to explain the motion of the moon, the planets, the planet's moons, comets, astroids, and other stars.

The point is, what is "obvious" and "simple" depends a lot on what you think and what you know and is by not necessarily universal.

Actually, I'd say that the simpliest theory is entirely dependant on what you know and is almost certain to change as you learn new things.

"Sure, one can argue that if two theories are functionally equivalent, there's no downside to taking the simpler one. But has anyone demontrated this logically or mathematically?"

It's really a postulate, an unprovable given. If the 2 theories are really functionally equivalent you must accept the simpler. The more complex one only wins if it can explain behaviour that the simple one can't. Then they aren't really equivalent, are they?

Assume for the moment that Einstein's physics and Newton's physics are functionally equivalent. Einstein's is more complex. If both came out in Newton's time, Einstein's would have to be rejected. Einstein's explains many things that Newton's doesn't - but back then they didn't realize that those things needed explaining. The only thing that could be pointed to then that Newton's didn't capture is slight misprediction of the orbit of Mercury. I'm not sure they could even measure it's orbit accurately enough to detect the misprediction back then. Not really good enough for Einstein to be percieved as more than a crank.

As time goes on more and more evidence accumulates that Einstein can explain and Newton can't. They become less and less equivalent.

Actually, yes, Occam's Razor can be considered to be a mathematical conlusion of Kolmogorov Complexity Theory.

Briefly, Kolmogorov Complexity Theory is the study of the compressibility of strings of symbols. E.g., consider the three 10 digit strings "0123456789", "4294967296", and "5286354993". Which is most compressible (or, almost equivalently, easiest to remember)? Well, the first is obviously easy to remember (compress): count from 0 to 9. The second is (not as obviously) perhaps even easier to remember (compress): it is 2^32. I believe the third to be difficult to remember (because probably it has to be completely memorized - I typed it in "randomly").

Now suppose we consider infinite strings instead of finite strings, and we consider all computer programs that print out the first n symbols of a given infinite string. In Komogorov Complexity, Occam's Razor is equivalent to the idea that the shorter the program that prints out the first n symbols, the more likely it is to print out the correct (n+1)th symbol. This can be made completely precise, and then "Occam's Razor" is a provable conclusion.

One way to think about why Occam's Razor is true: shorter theories are less likely to have arbitrary, extraneous features which imply incorrect conlusions (predictions).

well, let's see here. 4% of postulated matter in the universe is known to exist. 96% of postulated matter in the universe is NOT known to exist. that's a fine fudge factor to have in a test, and might explain where budget figures come from in the government:-D

it certainly explains where a lot of my assignments come from at work, lol:-D

What's the difference if dark-matter is really just another false theory? In the long run it's not going to make a whole heck of a lot of difference.

Actually it will make a huge difference. Just look at how Bohr's model of the atom changed chemistry and particle physics. Or how Plank's quantum theory caused a revolution in the physics community. And one of the most famous examples of an upset in scientific theory is Einstein's theory of Relativity verses the Newtonian theories most commonly held at the time.

Each of these theories caused an almost immediate revolution in their respective fields which spread out to similar disciplines. Fast forward 20, 30, 50 years or more and a number of innovations and inventions appear which stem from these theories. If these theories had not been introduced then we would most likely not have had such an explosion in technology.

Just because we wave our hands and say something is out there doesn't mean that we understand it or can use it. If we know the true mechanism behind dark matter and wether or not it is just "hand waving" then we can apply that knowledge to useful applications. For example, it is assumed that this dark energy exhibits a repulsive force similar to gravity but opposite to it in direction. If we truly understand how this works then we might be able to apply that knowledge toward "anti-gravity" spacecraft, etc. On the other hand if there is some other cause for the repulsion then we would need to know IT'S mechanism in order to utilize it.

In the end, science is the quest for truth, not convenience. Just knowing that there is a certain effect is not enough. Scientists are not looking to solve the question of "what is that" but rather "why does that exist and how does it work". That is why it is important to seek out the true reasons behind the dark matter observations.

And of course there are those New-Age whackjobs who think that in truth we are simply making the rules of the universe up as we go along.

I used to think it was crazy. But then I imagioned what life would be like for a process on a Linux box. In some respects, the system never changes. In other respects, as chunks of the system are refined an upgraded, previously famliar systems take on more complex, and at times, incomprehesible behavior.

A process would be oblivious to the universe stopping and restarting with a new kernel. (Assuming the system had a suspend-to-disk function.) You would only be able to understand the universe indirectly through it's behavior, not through reading it's source. And assuming you could read parts of the source, it is always being updated and revised.

It the process under Linux is too strange, how about a citizen under a government. Laws are just another form of code, and they too are every changing. Some parts are like the Constitution, broad in scope and largely set in stone. Others are like legal precidents, situation specific and sometimes arbitrary.

No one has bothered to even look to see if the rules by which our universe exists today are the same as a few million years ago, or a few billion years ago. How would you be able to tell that, say, the gravitational constant of the universe has been constant all along?

You are mistaken. There have been a number of studies done to try to determine if fundamental "constants" such as the speed of light are in fact constant.

It is, of course, very difficult to devise experiments to test such theories, but a number have been designed and performed. The phrase "no one has bothered to even look" comes up in other fields, such as paranormal research, and it is just as untrue there. Scientists would love to find evidence of (say) the gravitational constant changing, extraterrestrial organisms, or psychic power, and to suggest that they haven't even bothered to look is an insult to the field.

This is laughable. What happens if you live your live believing in the christian god, and it turns out that in fact the gods are norse? Or what happens if the test to get into heaven is that you didn't believe, that you didn't get faith?

I think AC, your post comes from one who does not get it, and by rushing to the defense of religion where no assault is being perpetrated, you miss the mark completely.

It is human nature to "know" how or why things are the way they are. You choose your explanation to be God. It is a nice and easy way to go about life, believing that everything has a purpose, but you do not need know what that is because you have God.

Scientists, on the other hand, have a driving desire to learn. This has nothing to do with "anti-religion" or a desire to prove there is no God. In fact, you may find that quite a few scientists do believe in God or a "creator" or what have you. They just don't try to use this "God" concept to explain away the unexplainable. They have been issued a challenge by the universe and they have chosen to rise to the occasion. My guess is because there is precious little left to explain, as most of our daily life has been easily described by science.

Besides, who is to say that what God is not the final answer to the Theory of Everything? Something tells me we are little closer to explaining how God works than we were a thousand years ago. What if science is merely an attempt to acheive a greater understanding of God?

As a matter of fact, yes.;)Some people get by fine on faith and that works for them. I've known many happy faithful people and I sometimes even envy that quality in them.But that just isn't how I work. I look at the world with an innate need to figure it out. This makes it impossible for me to take any religion literally.I suspect this is common with many geeks.

I always like this question and I think Descartes' answer is a cop out.In truth I can't. He said "I think therefore I am" but when you read his whole argument you see that it goes in a circle.The best I can do is say that it doesn't matter. I do think. The fact that I think may not mean that I exist (it could be your caffeine addled mind thinking I'm thinking). But it doesn't matter from my perspective. My only option is to go about my life assuming that I exist until I'm proven wrong. What is the alternative?

Pascal's gamble is weak at best. Clever man, stupid idea...it's easy enough to show that the argument is absurd simply by using it to "prove" that you should believe things that no one in their right mind should.

For instance...I walk into the room and tell you I'm Jesus and that I need you to perform some non-trivial task for me. You're not going to do it...you're going to assume I'm crazy or a con man. As well you should.

But the same argument for Pascal's gamble applies here and states that you should do what I say...just in case, because there's so little to lose and sooo much to gain.

Just remember what Pascal said: If you believe and you are wrong, you've at least led a good life; if you believe and you're right, heaven is on your way. If you don't believe and you're right, you've lived your life the way you wanted to; but if you're wrong....which outcomes pan out the best?

If I believe what? You tell me I'm going to hell if I don't believe in Jehovah...that guy tells me I'm going to hell if I don't believe in Allah...that guy tells me I'm destined for the land of Thud if I don't believe in Eris.

You also assume that I can choose to believe. Even though I try to believe six impossible things before breakfast, some propositions I just can't swallow - say, that Elvis Presley is alive and living on the Moon in a love nest with Marilyn Monroe. Or most of mainstream religious dogma.

Pascal's Wager is absolutely no help at all.

This of course ignores that if there were a deity that created beings, endowed them with the capacity for logic, failed to provide evidence of its own existence, then punished those beings that failed to believe in it, said deity would be sick and twisted, not deserving of worship but in need of intense psychotherapy. (Hmm, now that does sound like a believable proposition. "God's not dead, he's just very very sick in the head.")

Hmm... two references to the same Almighty, and one to a made-up religion.

So tell me, if I worship Jesus and it turns out he was just one of Allah's prophets, does he waive the "no other gods before me" clause? And if Jesus is divine but I worship Allah and deny that he was anything but a man, does Jesus forgive the mistake?

Saying that Allah and Jehovah are the same bloke is fine if you're talking about the mythologic tradition, but as a practical matter it doesn't quite work out.

If you convert to (say) Christianity to maximize your "expected return" from life, you're being a hypocrite -- unless you're very different than I am. I don't have a lot of conscious choice about what I believe -- it either happens or not. I do have a conscious choice about how I behave, but to act in contrast to my beliefs is, as they say, to be a hypocrite. No good: hypocrites don't get in to Heaven. In short, for me (and people like me), Pascal's Wager is a canard -- I don't get to choose what I believe, so the dichotomy isn't a real one.

It seems to me that a central tenet of Christianity is the Good News itself -- that an actual guy actually taught a bunch of people how to be good to each other, and actually came back from the dead. That is (at least in principle) a physical, provable proposition, and finding things like the shroud of Turin is a big part of that. Other religions work the same way -- there're a core set of beliefs that hold in the physical world, and that are thought to be supporting evidence for some metaphysical beliefs.

It also seems that this thread is pretty far afield from the topic of cosmology.
Religion and physical cosmology are somewhat orthogonal.

1) Pascal's wager doesn't work - lots of religions make countervailing or contrary claims to being correct. The question that most people have to decide is not whether to have faith in anything or not, but whether to believe in Christanity or Hinduism or Judaism or Islam or... Many of these choices are exclusive or contradictory, so believing in something won't necessarily save you - only believing in the right thing will. In addition, believing in something excludes options from the here and now - if you hold a religious belief, you must act consistently with it, excluding some possible actions that might benefit you. Pascal's Wager is not cost-free, and since its benefits are unclear (if all beliefs lead to the same place, Pascal's wager holds; if some beliefs lead to Hell (or some other bad place) then the value of choice may be much smaller and on the order or the cost of choosing and the opportunity costs of actions you cannot do), it isn't really a very good argument for religious belief.

2) Science and religion are not exclusive unless one forces them to be. Science takes a pragmatic view of the world - what effects we can observe or measure are those of consequence to science. The immeasureable is not science's purview. Religious beliefs ask different, perhaps broader questions: What are we doing here? What do we do with our lives? How does everything work? Science can be considered a subset of this. Multiple religious beliefs may be consistent with a physical phenomenon - the things that distinguish them exist in a place science can't get to and thus has no legitimate say in. The problems occur when religious and scientific claims occupy the same ground and are contrary. In this case, science usually wins because it can be tested, whereas religion depends upon claims that cannot be tested (but which can only be trusted).

In my opinion, it is not the "anti-religionists" who have betrayed us, but a subset of religionists. Religion and science have existed side by side for some time and were not considered inconsistent. In the last few hundred years, some religious folk have tried to "prove" their beliefs by misusing logic and science to their ends (creationism/intelligent design/creation science, for example). Trying to prove the unprovable only further hardens the demands of people for proof before they will believe, undercutting the faith; after all, if the people who claim to most strongly believe something require proof to believe in it, how much faith can they really have? There is also the bonus of trying to force people to have a faith whose value derives from chosen belief (thus destroying the object of belief for others). In addition, the likely purpose of the logical legerdemain (to compel others to behave as one would like) only serves to alienate those who would otherwise be quietly accepting of the faith of others. Vehement (and sometimes illogical) people who don't believe in religion probably come at least in part from this.

The underlying problem with this mindset is that (for the most part) religion relies upon faith - so there's no need to rely upon physical evidence.

Faith, at least according to the bible, is belief in something without seeing any evidence. How wise is that? Do Christian parents teach their kids to believe anything a stranger says? "Hey kid, your mother sent me in this van to come pick you up after school. I don't have any evidence to support this, but you have faith, right?"

Christians are actually proud of the fact that there is no evidence supporting their religion, then they go and get mad with scientists because there isn't enough of an abundance of evidence for them to accept evolution. Why are people willing to accept the existence of a supernatural being, despite a lack of any evidence, but they're unable to accept something like evolution because there might be some flaws in the massive amounts of evidence already supporting it?

Just remember what Pascal said: If you believe and you are wrong, you've at least led a good life; if you believe and you're right, heaven is on your way. If you don't believe and you're right, you've lived your life the way you wanted to; but if you're wrong....which outcomes pan out the best?

Sure, you can keep on believing in the God of the bible, but at your own peril! I am here to tell you about the Great Banana and I have my own wager to propose. If you believe in the Great Banana and He doesn't exist, you've at least led a good life. If you believe and you're right, you get a great reward of bananas. If you don't believe and you're right, then nothing lost. But if you don't believe and you're wrong, not only will you be continually ground up into banana tree fertilizer, but also all of humanity will too.

See, there's a much greater downside to not believing in the Great Banana than there is in not believing in the God of the bible. Therefore, since you're reducing everything to simple comparisons, it makes much more sense for you to believe in the Great Banana. Trust me. It's a very appealing religion, just make sure you don't slip in your faith.

When scientists look at the way that galaxies move through space, they see that many of them move a great deal faster (about a factor of 10) than theory predicts. Assuming that current theory is correct, the most likely explanation of these observations is that there is a great deal more matter in the universe than we can currently detect. If we can't detect it then it must be pretty much invisible across the EM spectrum, so scientists have christened it dark matter. Much effort has gone into trying to prove its existance but as as far as i'm aware there has not been too much sucess.

As I remember from my astrophysics class (and this was some years ago so feel free to correct me) there are two main candidates for dark matter, both of which have been tediously acronymed.

MAssive Comapact Halo Objects (or MACHOs) are basically chunks of ordinary matter, floating around in space that give off no radiation. Think brown dwarfs (stars without the necessary mass to initiate fusion). As I remember, most scientists are very sceptical that a significant amount of dark matter could be contained in MACHos.

Weakly Interacting Massive Particles (WIMPs- gotta love that scientist humour) are the other candidates and are hypothetical particles, heavier than neutrons, that were formed in the Big Bang and have been travelling through space ever since. As their name inplies they would have almost no interactions with normal matter and so by definition would be almost impossible to detect. Again there have been attempts to prove the existance of these particles, mainly involving mine shafts and a lot of water, and again there have been no conclusive results.

Now the significance of all this is that as you may or may not know, the universe is presently expanding and will continue to expand for some time. What will happen after that, however, is a matter of some confusion. One theory says that it will continue expanding forever (open universe) , while another says that the gravitational force of the matter in the universe will cause the expansion to stop and then a period of contraction to start, ending up with all the matter coming together in a 'big crunch'. This second theory creates what is known as a closed universe and people have postulated that the 'big crunch' is analagous to the 'big bang' that started the universe in the first place. In this way we get an infinite cycle of universes, each starting with a bang and ending with a crunch

(I am an astrophysicist. I am not a cosmologist, but I do galaxy evolution... we hang out with cosmologists)

There are quite a few pieces of evidence for dark matter:
- internal dynamics of galaxies: when you look at how fast the outer parts of galaxies move around the central parts, you find that the amount of mass necessary is much more than what you see
- dynamics of galaxies in clusters: when you look at how fast galaxies move around in galaxy clusters, you find the amount of mass necessary is much more than what you see
- non-linear growth of primordial perturbations (sounds complicated, isn't really): the universe used to be almost completely smooth. now it's filled with clumps of matter like galaxies and clusters and big voids without much matter. the structures collapsed because of their mass. if there were only as much mass as you can see, there hasn't been enough time for galaxies to have collapsed

The amazing thing about all of these measurements is that they all give you the same answer for how much mass is really out there.

It isn't really amazing that they all give the same answer, because they all make the same assumption:

f = G.m1.m2/d^2

What if this is only a *very* good approximation for all normal purposes, and even for things as large as the solar system (in the same way that Newtonian mechanics is good enough for all earthly based stuff).

What if gravity doesn't quite work this way at galactic scales?

There was a piece in New Scientist last year making this exact point, and the researcher was able to explain most effects that are otherwise explained by dark matter, by slightly changing the theory of gravity.

Einstien did it for Newtonian Mechanics.

The real problem I see here is that the scientific method has been largely ignored. We observe the universe, we devise theorems to explain it, we test the theorems against other observations. If the test doesn't match reality, we assume that the theorem is wrong.

This doesn't occur with cosmology.

We observe the universe, we make theories, and when they don't fit, we assume there must be something wrong with the universe!

It will be interesting to see how scientists who have staked their entire careers upon the existence of dark matter would react to the discovery that it does not in fact exist. Ideally an invalid theory is dropped, and a new, more "correct" theory is created. However, I have a feeling that a lot of people have invested too much time and effort into dark matter to let it go without some serious evidence.

Five years ago, every cosmologist "knew" that the universe was flat and matter supplied the critical density (in other words, no dark energy, that 70%). Conventional wisdom has completely changed with the discovery of the accelerating universe.

If the data is there and convincing, the views will change. But any alternative theory is going to have to explain all the observables, not just the two mentioned in the artice.

Five years ago, every cosmologist "knew" that the universe was flat and matter supplied the critical density (in other words, no dark energy, that 70%). Conventional wisdom has completely changed with the discovery of the accelerating universe.

No they didn't. I hung out with cosmologists when doing my astrophysics PhD over 10 years ago, and they were considering various mixes of hot and cold dark matter, dark energy, open and closed universes. Flat universe and no dark energy was merely the provisionally accepted most likely solution.

The implied existence of dark energy is revolutionary to cosmology, but it didn't catch people by surprise - they were actively looking for it.

But kludge's are the black eye of science, and even really bright people can make them (remember Einstein and his cosmological constant?).

To be fair, the cosmological constant was a constant that emerged naturally from the derivation of General Relativity, with no indication of what its value should be. To apply it to reality, some value had to be assumed or determined. The simplest thing to do would have been to arbitrarily give it a value of zero, but that would have implied an expanding universe. In the absence of evidence for expansion, Einstein chose to give it a value that made the universe static.

Sorry to let you know but making kludges is really how alot of new physics is done. Someone finds some kind of 'kludge' that models reality, then the theorists try to explain it in terms of basic laws.

Lots of things were done this way. Specifically, Planck's attempt to correct the ultra-violet catasctrophe of black-body radiation theory by quantizing the radiation was a total kludge. The theory matched the data fairly well, which led to a flood of new inquiries, leading to Einstein's description of the 'photoelectric effect' and the birth of quantum mechanics.

The concept of the gyromagnetic ratio, or Lande g factor, for particles was another kludge that can be adequately explained using sufficient detail of Quantum Field Theory.

Even more macroscopic phenomenological theories, like Landau's theory of 2nd-order phase transitions expands the free energy of a physical system in terms of one or more order parameters. That's a kludge and a half, but in many cases adequately describes physical systems close to phase transition points that formal Hamiltonian interaction methods cannot get to.

Extending on this is the Ginzberg-Landau theory using a complex order parameter for superconductors. (Remember Ginzberg just won the Nobel Prize for Physics a few months ago. Landau won it decades ago and would have won it again if he was alive). It was shown by Gor'kov that the BCS theory of superconductivity (ie, formally-applied theory involving Cooper pairs of electrons and superconducting gap) approaches the Ginzberg-Landau expansion at the critical point.

So yes, Kludges are really used all the time in physics, and they're no black eye at all. There's two reasons we need to use these. Firstly - macroscopic systems are just so damn complex one cannot solve a 10^23 dimensional Hamiltonian, that's ridiculous. So even from basic principles complicated order can emerge.

The second reason is that it is quite likely we don't fully know the ultimate physics basic building blocks, just a very good approximation of them. Complicated systems can reveal small perturbations from the standard model that's accepted.

Entire careers in physics are going straight down the shitter because of dark matter, because it doesn't exist. From the very first time I read about it, I thought "Geez, this sounds like a 3 year old trying to cover up the fact that he doesn't KNOW the reason why".

Uh.

The primary evidence for dark matter is that if you look at how galaxies move and how clusters of galaxies move, they should all be flying apart. They are moving too fast for the amount of gravity we calculate by adding up all the mass of the stars and the gas that we can see. Since galaxies and clusters are around all over the place, we know they're not falling apart. Ergo, there must be more gravity than can be accounted for from the material we can see.

The simplest, easiest, and most direct explanation is that there is more there than we can see. Matter not emitting light, thus called dark matter. There's nothing kludgy or ad-hoc about this, it's the most natural conclusion to make. The alternative is that Newtonian Gravity (or General Relativity, which has Newtonian Gravity as a limit in the relevant case)-- that theory which perfectly predicts the motions of planets, spacecraft, apples, and other things that we have lots of experience with-- must be wrong. There are people who believe this over Dark Matter, in fact, but to me, "stuff there that we haven't found yet" seems to be a much more likely and plausible explanation.

The evidence for why the dark matter can't all be baryonic (i.e. made up of "normal" stuff) is more indirect, but it comes out of other theories for the construction of the elements in the hot early Universe-- and this other theory itself has made predictions that match well what was observed.

A theory of how things work is only as good as that theory's predictions. Ptolemy's model must have been very useful for predicting the position of celestial objects or it would have been put aside even 'longer' ago. It's only when a model is in direct conflict with observed data that it is in trouble: even if there is no formulated model that works with the new observations.

'Dark' energy and matter will only be in serious trouble when that model no longer explains observed data.

No, Relativity (neither the Special nor General theory) says that "everything is relative". Special Relativity says that inertial motion is relative in flat spacetime (i.e. in the absence of gravity). This is another way of saying that all inertial coordinate reference frames are equivalent. (Special Relativity says more than that, namely that light propagates at the constant speed 'c' independent of the motion of its source. This is what separates Special Relativity from Galilean Relativity.) General Relativity says that *locally*, accelerated motion is equivalent to inertial motion in a gravitational field. (The "locally" part accounts for the fact that the gravitational field lines are not parallel, but converge on the gravitational source.)

What this boils down to is that circular motion is accelerated motion, not inertial motion, and is not simply relative, and spacetime is not flat surrounding bodies that planets orbit. So no, Relativity does not validate the epicycles theory.

No. The fact that any inertial frame of reference can be regarded as equally valid does not begin with Einstein, it's fundamental to the way all physics is done. Einstein's insight was that regardless of your frame of reference, light appears to always be travelling at the same speed relative to you.

The key word here is inertial. An orbiting body is accelerating towards the center, and is therefore not an inertial frame of reference by definition. As far as calculations on the surface of the Earth go, non-inertial effects (also present because of Earth's rotation) can generally be ignored for comparatively small times and distances without significant loss of accuracy, but on the scale of the Solar System and other systems where celestial mechanics are employed, they cannot be ignored. Epicycles introduce a new non-inertial component, and therefore can't be regarded as merely relative.

...but doesn't String Theory tend to suggest that "dark matter" isn't actually dark matter, but instead is gravitation bleeding from other universes? The same theory also explains why gravity in this universe is so weak. Because most of it bleeds of into other universes via the higher dimensions, it's weak enough for you and I to move our limbs.

That's what I love about physics: it's so out there that you'd think the person who just said something like that was smoking crack, if he didn't have a PhD.
Gravity bleeding between universes...
Who needs science fiction?

There are current astrophysical models which postulate that the Universe is a hyperplane embedded in higher dimensional space, called Randall-Sundrum models. In which case gravity can propagate trasverse to this plane, hence there can be matter outside the Universe which can still interact with it. There is also the idea that this 'brane' (as it is called - nothing to do with zombies) has a small extra dimension (less than 1mm in size) so the current gravitational law needs to be changed to r^{-4} or so at very short distances.

String theory as such tends not to comment on dark matter (could be D0-particles, could be fish) as no-one knows how to compactify it down from 10D and break supersymmetry in a useful way.

Gravity is weak in the short-range when compared to the three other known forces of nature. The four forces are gravity, electromagnetic, strong nuclear, and weak nuclear. Gravity is an attractive force between all matter and energy, electromagnetic is an attractive and repulsive force between charged particles and magnetic fields, the strong nuclear force is what holds together protons and neutrons in an atom's nucleus and the weak nuclear force is what mediates electron and positron decay.

If you set the strength of gravity equal to 1 then the other forces have the following approximate strengths relative to gravity:Strong nuclear force: 10^40Electromagnetic force: 10^38Weak nuclear force: 10^15Gravity: 10^0

So why is gravity so important if it is so weak? The thing about gravity is that it falls off slowly with distance and it can't be negated or blocked (as far as we know). Other forces are either extremely short-range or, in the case of the electromagnetic force, have both an attractive and repulsive component that tends to cancel out in the long-run.

We don't understand something fully? Wow... that's about as brilliant as deciding to cut my sandwich in triangles instead of in squares.

The truth is this. We have such a little understanding of actually governing laws that we can't begin to fathom it. However, that doesn't stop us in progression to learning. Just because this theory might not be right (and probably isn't) doesn't mean we are any less an idiotic species. We've been working on these theories for many millenia. One of them turning out to be wrong won't be a surprise... it's a probability. Without the wrong hypthosesis, we can never stumble onto the correct ones. Its Edison's, "Every time I fail, I know one more way how to NOT build it" idea.

There seem to be growing "hints" that something is wrong with current theories about the very nature and behavior of gravity. This includes alleged dark matter that cannot be identitied, planetary space probes with slight deviations from expected sun "pull" [1], and the fact that there is no identifiable "negative" gravity while the other forces do have negative values or particles.

[1] It was originally thought that heat generated from nuclear fuel cells was "pushing" the probes, but this was mostly ruled out because the heat lessens over time, but the pull was constant.

There are several plausible candidates for dark matter. There are lots of suggestions from particle physics that every particle we know now has a partner. This theory is called "super symmetry" and the lightest of these particles may be stable (and many times heavier than a proton).

This question we may actually know the answer to in a decade or so when the LHC comes online and is producing results.

Science has been progressing on the basis of constantly proving theories as kludges and bringing about something newer and more real. Imagine if our currently held view was true (before Standard Model), we will never be able to travel faster than light, we'll never harness energy bigger than a hydrogen bomb, we'll never really travel far beyond the Solar system, travel back in time etc.

Before the cannon was invented everyone thought the arrow was the greatest weapon, and few could really predict the power of "Little Boy" on Hiroshima. Quantum Mechanics has given us so much hope, of unknown and unexplainable realities, and that far more is possible than we first thought. It means the road before us is much longer, but far more interesting. I'd prefer it that way.

Welcome to the world of neuro-bio! Whoever built our brains didn't know jack about maintainability. They're a bloody mess! Unused functions left around from previous versions. Disabled features. Appalling code reuse. Oh sure, there are some beautiful optimizations, and the system architecture has a certain elegance -- but the implementation is crap.

If an omniscient power built us, I hope He/She wrote in a high-level language and then compiled with some heavy optimizations turned on (-oGOD?). If They were hand-rolling this shit, I'd like to have a word or two with Them.

The keynote speaker [siggraph.org] at the 2003 SIGGRAPH conference in San Diego was the British astrophysicist Anthony Lasenby. He claimed that a new kind of unified Euclidean and hyperbolic geometry could explain acceleration and deceleration in the Big Bang. He was talking at SIGGRAPH because his new unification of geometry is supposed to be more elegant for computer graphics modeling than the current homogeneous coordinates now used. He wrote a book [amazon.com] about the geometry. But I have been unable to find a paper relating to the cosmological application on the web.

This is not the first time geometry has been used to unify and simplify physics. Previous examples are Galilean coordinates, special relativity, and general relativity.

Bringing this up without mentioning M.O.N.D. is irresponsible journalism. MOND (Modification of Newtonian Dymanics) is a theory that simply says that gravity 'decays' at a slightly different rate than expected over astronomical distances. The effects predicted by this theory are spot on to the observed effects that dark energy and matter try to explain.

I googled about found this link [umd.edu], but I first read about it in New Scientist about a year ago.

I may be showing a few gray hairs here, but revolutions in the sciences have occurred in my lifetime with scientists adapting fairly well. The first was the acceptance of Big bang in the late 1950s. Between 1927 and 1955 the Big Bang was just one of several "equally attractive alternative theories" which included the eternal-infinite universe and continuous creation of matter. The microwave background and the abundance of helium brought the big bang into the fore front.

In the 1960s the quark unification of subatomic particle became the predominate theory. Plus quantum electrodyanamics was verfied in high energy experiments to extremely high precision.

Also in the 1960s plate tectonics replaced an up-and-down explanation of geologic forces.

If the evidence suggests a more powerful theory, then physicists will revise their theories again. Science does not stay attached to incorrect theories (though block-headed individuals do).

I may be incredibly naive, but it has always bothered me that we insist on believing there are only 4 types of force in the Universe, each operating on widely different scales. Why can't there be other forces that operate on too large a scale or too small a scale for us to observe? Is the postulate of "dark force" effectively a theory about a fifth type of force?

Well, a force that we could never observe, we could never test the existence of. Sure, you could postulate it, but it wouldn't help the theory at all -- you wouldn't be able to tell if your theory was right or not. You might as well say that tiny invisible demons are causing strange things to happen...

I love the Economist as much as the next person, but in this case the search for "controversy" badly mischaracterizes the current state of our understanding of the universe.

First claim: Analyses of the WMAP data on the cosmic microwave background (CMB) show correlations with galaxy clusters that indicate the official analyses of the data are wrong. I find this highly unlikely. First, the effect of the hot gas in those galaxy clusters on the CMB is well known - it is called the Sunyaev-Zeldovich effect and perturbs the spectrum in a well-known way. Second, the official fits to the WMAP data use a consensus cosmology model with about 12 free parameters to fit a dataset of more than a hundred points... beautifully. Third, the consensus cosmology itself has been built up out of a huge array of other observations (supernova distances; Big Bang nucleosynthesis; the "weighing" of galaxies and galaxy clusters; the age-dating of globular clusters), all of which were pointing to the existence of dark matter (even within our own Galaxy!) long before WMAP was even launched. Fourth, modern theories of particle physics also give us good reason to expect the existence of dark matter particles, independent of any astronomical observations whatsoever. So WMAP has simply been the final nail in the coffin, and anyone who wants to overturn dark matter and dark energy has a great deal of additional work ahead of them.

Second claim: Measurements of the masses (actually, the luminosities and temperatures) of high-redshift galaxy clusters indicate a high fraction of baryonic mass, removing one of the justifications for positing dark matter. This finding is even more fishy-sounding. To understand this, realize that the group in question has deliberately chosen the most-distant and therefore hardest-to-study clusters to study, and adopted temperature-mass relationships that are calibrated in the local universe (and may not apply at these great distances) in order to find that their sample differs from the standard model predictions. Without even bothering to list all the ways in which they might be wrong, let me simply state that even if they are right there is a lot of independent support for the dark matter + dark energy picture that neither of these groups is addressing.

Rather than distract yourself by trying to figure out why the carefully constructed consensus cosmology might be wrong, then, I think it is more useful to examine the remarkable ways in which it has been proven right in the last few years. Altogether it is truly a wonder of the modern world - even if it may at some point be shown inadequate to the universe we live in.

It is doubtful that the entire theoretical edifice of dark matter and dark energy will collapse all at once (in the way it might more reasonably have been said to have happened for the electromagnetic aether.)

In particular, dark matter, though incredibly mysterious, is probably on firm enough ground that it will withstand a series of challenges. Galactic rotation curves and measurements of cluster temperatures both give very strong evidence for dark matter on vastly different scales; in addition, it is difficult (OK, fine: downright impossible in standard Einsteinian gravity) to get any kind of structure to form *at all* in the universe if one is only allowed to use the visible matter. The precise ratio of dark to visible is definitely up in the air; and, of course, there are competing models that modify gravity -- if these matured enough (they may already have -- I haven't kept up) to make predictions on a wider range of scales, they might work as well.

Indeed, a lot of gravity modifications (extra dimensions, etc.) behave *phenomenologically* as if there was dark matter -- so all the effort we've put into simulating dark matter may not be in vain after all, even if Einsteinian four dimensional spacetime is not the name of the game.

In contrast, indeed, is the exact count of the "baryons" (ordinary matter.) I would be very surprised if we were off by a factor of (lets be ultra-conservative here) five in the baryon number, which is constrained very well by big bang nucleosynthesis, whose predictions remain in the "ordinary" realm of nuclear explosions. Something we know a little about.

The real mystery is "dark energy." There, the evidence is a lot shakier. It rests on a few pillars. There is a theoretical bias that wants the universe to be flat (so that the missing mass-energy is made up for by some dark energy component that doesn't cluster and affect our galactic rotation curves.) There are some really excellent (but difficult) measurements of universe acceleration, a signature of dark energy, from people who observe distant supernovae (these provide "standard candles" that allow you to measure distance given an apparent brightness.)

Finally, there are the CMB measurements, which provide a similar kind of distance measurement, but are open to alternative interpretations (instead of measuring apparent brightness, they measure apparent angular size -- but it is perhaps possible, if you squeezed around, to construct a different model where the apparent angular size is squished in odd ways.)

And then there are a host of other measurements that one might call more "marginal" (without prejudice to the people who work very hard to do them -- I aspire to be one of them.) They rely on a few more astrophysical assumptions, and perhaps would not convince the slashdot skeptic. (My profound apologies if I've missed out someone's awesome measurement.)

One big "trouble" is that we haven't seen good evidence for a very particular signal that one would associate with the simplest model of dark energy. (This is the "low quadrupole" -- the news stories you read about finite universes are from people who, in part, are motivated by the desire to explain this low quadrupole signal by other means.) Of course, it is entirely possible to make more exotic dark energy models that don't show this signal (I've coauthored a paper on one such model), but that missing signal, gosh, damn.

The Economist is usually good with science articles, but it really kind of missed the point on this one. Shanks et al. are not "bringing down the whole edifice"; they are pointing out what they see as a possibly problematic signal in the CMB data. This may inspire in some a little additional -- and very healthy -- skepticism about the dominant models. But it is important to mention that there really is no "dark energy mafia"; nearly any astrophysicist worth his or her salt would drop dark energy like a stone if the evidence started piling up, and many, many astrophysicists keep a hand in alternate models that don't rely on dark energy because, hey, what a scoop that would be.

At least they have observations. And astronomers in general are a genial bunch. Anyone who finds (and this is the most likely case) that there is dark matter, but not nearly enough of it, is assured of nothing more that a few years of ostracism before enough new scientists come into the field who don't have the same emotional investment in dark matter theories.

Compare that to the potential fate of the poor wretch who disproves the Riemann Hypothesis, and undoes almost all progress in pure mathematics since the beginning of the 20th century. I know for a fact that there is a basement in Cambridge [cam.ac.uk] where this person will live out their days being forced to review unsolicited "proofs" of duplicating the cube, trisecting the angle, and squaring the circle.

Dark matter is simply a theory. If Newtonian mechanics is correct (we don't even need to worry about relativistic corrections here), and the laws of physics are the same everywhere (a fundamental principle of science), then there is a lot more matter than we can see (i.e., that is glowing). We can tell this by looking at the rotation curves of galaxies, and even the behavior of clusters of galaxies. There must be a lot of matter there that we can't see, if Newtonian mechanics is a reasonable approximation. It's called dark matter.

Dark matter in and of itself is really not a revolutionary concept. In most wavelengths of light, for instance, you qualify as dark matter (you emit no visible light, although you do emit infrared radiation, so you're not completely dark matter). Look around your room or office. How many things emit electromagnetic radiation. Your computer and your monitor, sure. Your light fixtures and other electronic equipment either emit light or heat. But most of the stuff around you emits internal radiation. A pen is dark matter. A cup of dark matter (once its reached thermal equilibrium, of course). That book is dark matter. The concept of dark matter is not only not revolutionary and mind-blowing, it's downright mundane. Given the survey of stuff in your office/room, is it any surprise that most of the junk in the Universe doesn't emit radiation on its own?

When we start getting into the weird realms of dark matter is when we start applying the Standard Model and find out that it doesn't seem like all that dark matter can be explained by baryonic matter (basically, protons and neutrons -- what we would normally consider matter). That's where things start getting sketchy and speculative, although we have some theories about what might be responsible. But dark matter in and of itself is simply a consequence of the mediocrity principle (that is, the laws of physics operate elsewhere just the same as they do here) and Newtonian gravitation.

All the popular media's fascination with dark matter is only so much hoopla.

You take the facts, come up with a working theory that fits the facts. As more facts come in, you continue to test your theory against the facts. When too many anomolies show up, it's time to come up with a new theory.

And there is nothing wrong with that. Is Newtonian physics worthless just because it couldn't explain everything? No, but we had to be willing to look for new answers when we began to see evidence that the old answers didn't work for everything we observe. It's called a paradigm shift.

Let's say our limited perspective from our solar system were somehow enhanced by a telescope/sensor at a neighboring solar system. Wouldn't this give us a much more accurate map of the universe than our current narrow view? For all we know most of the matter might not be visible because something is standing between us and it. The very fabric of space gets distorted by the weak gravitational field of our small star and each and every bit of matter floating around out there and we believe that larger gravitational forces exist, like black holes. If we can't even completely understand how and why our star warps the fabric of space how can we expect to KNOW the universe and all the matter contained within it?

We don't understand the laws of this universe. We've barely been able to explain it with simple mathematics. The universe, for all we know, might require higher mathematics than the human brain can easily comprehend. And what if there are other universes? But what do I know, I'm just one small voice in this titanic harmony-challenged choir. I'm sure one day someone with a lot of money will figure it out and tell all of us about it in an infomercial late at night on TV.

This thread misses an important point. Even though Ptolemy's theory was wrong, it was a lot closer to the truth than previous ideas like "the lights in the sky are gods with flashlights." The point is that even theories that are wrong add to our knowledge by providing a starting place for deeper inquiries.

It's more than that.
If Dark Matter doesn't exist, we will be forced to re-examine more than just our current picture of the universe. Galactic Rotation curves, velocity dispersions of galaxy clusters, the flatness of the universe implied by the CMB, type Ia supernovae data, as well as other distance indicators, all imply that the parameter "Omega_mass" (the mass density of the universe divided by the critical density) is about 0.3.
If there is no "dark matter", we don't know how to explain this number. Baryons, i.e. stars, planets, gas, etc., make up only an "Omega" of 0.044 +/- 0.009. This constraint is from Big Bang Nucleosynthesis and is very strong. Although there are plenty of open questions about dark matter, it seems to me (just an astrophysics grad student) that there is an overwhelming amount of evidence for not only dark matter, but the model of "cold" dark matter as well.
None of the alternatives can explain even half of what Dark Matter can, including modifying gravity. Plus, Dark Matter is consistent with GR, the big bang, and everything else we hold dear about physics and astronomy, whereas other theories don't.
Just my two cents...
Ethan

Would someone please translate this and tell me what the hell is being said?

"Nobody knows for sure whether Dark Matter exists or not. But there are a whole lot of independent reasons to believe it exists, all of which result in very, very similar numbers for how much Dark Matter there is. If the Dark Matter theory is wrong, it's very hard to imagine what else could possibly explain all those numbers, all at once. (It's easy enough to explain one or two of those, but that's not an improvement over current theories, that's a step back.) Dark Matter hasn't made it to 100% certainty, but other theories have a lot to explain if Dark Matter doesn't explain what we're seeing."

I think that's about right. I Am Not A Physicist, but I follow this and generally understand math, so I think I'm at least competent to translate...;-) (Perhaps Pi_0's don't shower would like to confirm/deny this translation?)

(On my own, I'd note that giving how flexible geometry can be, I can easily imagine someone constructing a geometry of the universe that doesn't need dark matter that turns out to be mathematically equivalent to a universe that does have dark matter. I'd give some of the geometry-based theories some time to be vetted by real astrophysicists before assuming they provide a real alternative; they may well just encode the Dark Matter into the structure of the Universe itself, which really isn't an alternate theory, just a restatement of the original in a different form. Until someone produces some Dark Matter, or the Universe is explored to our satisfaction to determine no such matter exists, this may remain unresolvable.)

Galactic rotation curves: If you have an object that rotates, and you know the velocity as a function of radius, you should be able to get the density as a function of radius. This is obvious, because the velocity is coming from gravity.

The problem: you can also get the density by assuming that light-emitting material carries the majority of the matter (stars - pretty good approximation) and then looking at the luminosity as a function of radius (how bright it is). So, in a perfect world, these two profiles would match.

They don't. Therefore either

Not all of the matter is light emitting

Gravity doesn't work.

Option 1 there breaks the least physics, so it's preferred.:) There are also other concerns - namely, there are some galaxies that do rotate correctly, and some that don't. So either gravity sometimes works and sometimes doesn't work, or option 1.

Velocity dispersion in clusters: See above - just with galactic clusters, rather than galaxies. Note that fixing one of these problems would probably fix the other!

Anisotropy of the CMB: This one's tougher to explain easily. 100,000 years after the Big Bang, the Universe was an extraordinarily uniform big fireball. Extremely uniform - because electrons hadn't cooled enough to form hydrogen yet, so it was one big hot plasma.

When hydrogen cooled, the photons in the Universe suddenly found themselves free to move, because hydrogen can only absorb certain wavelengths, and free electrons absorb continuously. Those photons are the Cosmic Microwave Background. Their uniformity is a very good indicator that the Big Bang theory is real - at least, from 100,000 years after the Big Bang to now.

However, matter that was in that fireball DID distort the radiation slightly - through gravity. And so we see anisotropy (nonuniformity) in the microwave background, and it looks very much like standing waves in the sky. The ratios of the strengths of certain frequencies tell us the ratio of dark energy ("lambda", the cosmological constant) to matter, AND also tell us how "flat" - i.e., how much total energy - the Universe has. It's flat. Exactly. Really really flat. It has exactly as much energy as would be needed to reverse the initial Big Bang (if it were all in matter, which it isn't). And it also tells us that dark energy is 70% of the energy content of the universe, and matter is 30%.

Big bang nucleosynthesis. BBN basically says "you can only get this much normal matter from a big bang explosion cooling to form atoms". It's amazingly accurate so far - it gives great answers for the ratio of certain elements, for instance. But it also puts a stringent limit on the amount of normal matter, of about 5%. The CMB *also* gives this same measurement - and, amazingly! - they agree! There are in fact even OTHER measurements which give values consistent with this number - 5% - so it's hard to imagine how measurements coming from completely different areas of physics (one is standing waves in the early Universe, one is nuclear physics) could give the same answers, and both be wrong. (But Nature can be perverse...)

So, Omega_m has to be about 30%, and Omega_b is about 5%. Plus there has to be something making stars and galaxies rotate too fast. Physicists, wanting elegance, say "two problems, one solution is a great theory."

Basically: If dark matter doesn't exist, we've got a lot of work to do to come up with other models, and a huge amount of it would affect gravity, which we thought we were beginning to understand!

It's very hard to imagine a form of gravity which could answer all of these problems, AND still be consistent with what we observe today.

Just to show another angle (as opposed to the highly doubtful statement that only 7% believe in God), I Googled and found:

In the US, according to a survey published in Nature in 1997, four out of 10 scientists believe in God. Just over 45% said they did not believe, and 14.5% described themselves as doubters or agnostics. This ratio of believers to non-believers had not changed in 80 years. Should anybody be surprised? (from http://www.guardian.co.uk/life/feature/story/0,130 26,1034872,00.html)

So no, it's not most scientists, as it's mostly half and half (according to Nature/Guardian).

Yes, exactly. That evolution occurs is a fact which can be demonstrated. On the other hand, the theory, which tries to explain how evolution works, could be inaccurate/wrong. The theory itself may change many times and might be completely overhauled for some new radical explanation. However, regardless of whether or not we understand the mechanisms behind it, nothing can change the fact that evolution exists.

In Britain, there are two types of gull which appear to be different species, a white herring gull and a lesser black-backed gull. They are quite different in appearance and do not (directly) interbreed. They are currently considered one species, though, because they share genetic material indirectly. The white gulls breed with the North American gulls and the black-backed breed with the northern European gulls... which, as you go around the world's northern edge, gradually change characteristics to become the other. Each local population occasionally breeds with its adjacent areas' slightly different gulls, and these small changes add up, until around the Alaska/Siberia area the gulls are roughly intermediate between the two types of gulls as found in Britain. There's no clear place to draw the line separating the spectrum between the two ends of the ring to separate those ends into two species.

If all the herring gulls in North America and/or Asia were to die due to some natural disaster (or to human interference), the white herring gull and lesser black-backed gull in Britain would become different species. In a sense this is a situation where the gulls have in most ways already evolved into two species, and could readily become two species given particular natural events. This type of species is called a ring species. [colorado.edu]

What do you mean absence. Look at dogs. We took wolves and turned them into a wide variety of shapes and colors from Great Danes to Chiwawa's all within the last 40,000 years.

The same is true with almost any domesticated animal. For pete's sake the entire science of animal husbandry is application of Evolution, just under our control.

Of course, our efforts in domesticating animals show that one force seems to be required to really make evolution work properly: a regulator. Someone who reviews what's good, what's bad, and what is really cool, though unexpected.

Next time some god-boy goes on a rant about how evolution doesn't exist, quote the parable of the Wheat and the Tares. In it Jesus talks about how God can't really tell what is useful and what is not until it has had a chance to develop. Once it is clear what is good, and what is not, someone comes by and clears the crap out.

> Evolution, OTOH, has never been demonstrated or shown in an experiment. To demonstrate evolution would require watching a planet from start to finish, which we have not yet done.

Sorry to inform you, but science allows indirect evidence as well.

> Something not taught in school that should be is that evolution is dependent upon natural selection, but not the other way around. The earth could have been populated by God/Aliens/someone creating species in a test tube somewhere and populating the earth. Natural selection would just as easily occur with this hypothesis.

You seem to be confused about the subject matter. It is correct to say that it doesn't matter whether gods/aliens/naturalforces/blindchance created life, because evolution could operate on the result regardless of the origin. All evolution requires is imperfect self-replicators.

> BTW, I'm a scientist

You certainly don't talk like a scientist. What is your field, and where can we find a list of your publications?

> WRONG. There is no such thing as proving a theory right (i.e. as truth).

And a real scientist would know that scientists don't spend their time trying to "prove" theories right. Rather, scientists look for explanations for observed phenomena, and theories are the product of that endeavor.

> Evolution is so mathematically improbable that I'm surprised that most scientists just accept it.

Can you show us the math on that?

> It's a great theory to explain things right now (which is why we use it), but there's a good chance it will probably be proven false someday.

Can you show us the math on that, too? (I'll gladly accept "it may be proven false someday", but you are asserting more than that, even with your double qualification. What are the chances that the theory of evolution will be proven to be false some day?)

You can only make mathematical proofs if you accept some set of axioms that themselves cannot be proved (and thus must be taken for granted) as the foundation for your proof. As for 1+1=2, it can be proved directly using the basic axioms of arithmetic which neither are hard to understand nor require 300 pages to express.

Slashdot posts about mathematics are usually so far wrong that I don't even try to respond to them. It is really distressing to me (having a Ph.D in mathematics) to see how shallow the general level of mathematics understanding here is.

However in this case your comment is only slightly wrong and therefore I have some hope that my reply might be a useful contribution.

You are correct that mathematical proofs are based on axioms. However there is still a crucial difference between a mathematical proof and a scientific theory. A mathematical proof is an absolute certainty. Note that I am not claiming that the underlying axioms are certain. I am only claiming that the proof itself is certain.

To put it another way, mathematicians are never certain about their underlying axioms but they are absolutely certain that if those axioms hold then the result stated in the proof also holds. It's kind of like a building with indestructible walls but no foundation.

Scientific theory is a whole different kettle of fish. You cannot prove a scientific theory with absolute certainty. In fact it is not even clear to me how one can define certainty within the framework of the scientific method. You never have any guarantee in science that future observations will be consistent with past observations.

In science you can prove a theory in the sense of preponderance of the evidence. You can even sometimes prove a theory beyond all reasonable doubt. But there is no way to eliminate the unreasonable doubts. Any endeavour based on empirical observation suffers from the fundamental limitation that you can never be sure of the next observation.

Finally, regarding 1+1=2, the foundational proof of this fact using the standard propositional axioms of mathematics really does require 362 pages. You can see the 362nd page on the bottom half of this Russell's paradox [cut-the-knot.org] site.

Looks like we're gonna have to stick some moldy olives in a freshly-killed goat and bury it in the sand for 48 weeks. Then we dig it up and soak it in the blood of a 3rd-born virgin girl. If the goat's eyes turn pink, God will give Lyndon Larouche syphilis, if they turn purple, dark matter exists. It's not the cleanest proof, but I say we give it a shot.

There is no decent explaination... emergent intelligence...it may explain why things can be completely random at a quantum mechanical level, but balance out in larger systems...

It's called the Central Limit Theorem and Superposition. You've got billions of identical particles (low variance), and a huge sample size at macroscopic scales, thus your mean (likelyhood of "expected" things, the precision, and thus "intelligence" in systems) will be pointy as a pin.I am 100% dead serious.

Perhaps maybe your REAL question is "why are quarks so damned sticky, protons so stable, and h_bar conveniently small?" because that encapsulates the huge gap between the quantum world and the stable world we live in.